C++ functions to convert an int to a C string and back again

intToStr.cpp

char* intToStr(int value)
{
    int divisor = 1;
    int bufferLength = 1;
    int isNegative = 0;
    int bufferIndex = 0;
    
    // Handle the negative value case by remebering that the number is negative
    // and then setting it positive
    if(value < 0)
    {
        isNegative = 1;
        value *= -1;
        bufferIndex++; // move 1 place in the buffer so we don't overwrite the '-'
    }

    // Determine the length of the integer so we can allocate a string buffer
    while(value / divisor >= 10)
    {
        divisor *= 10;
        bufferLength++;
    }

    // Create the resulting char buffer that we'll return.
    // bufferLength + 1 because we need a terminating NULL character.
    // + isNegative because we need space for the negative sign, if necessary.
    char *result = new char[bufferLength + 1 + isNegative];

    // Set the first character to NULL or a negative sign
    result[0] = isNegative == false ? 0 : '-';
    
    while(bufferLength > 0)
    {
        // ASCII table has the number characters in sequence from 0-9 so use the
        // ASCII value of '0' as the base
        result[bufferIndex] = '0' + value / divisor;
        
        // This removes the most significant digit converting 1337 to 337 because
        // 1337 % 1000 = 337
        value = value % divisor;
        
        // Adjust the divisor to next lowest position
        divisor = divisor / 10;
        
        bufferIndex++;
        bufferLength--;
    }
    
    // NULL terminate the string
    result[bufferIndex] = 0;

    return result;
}

strToInt.cpp

// Assumes the incoming char* is null terminated, the function does not modify
//  str.
// Assumes a positive number is *not* prepended with a '+' character.
// Assumes a negative number *is* prepended with a '-' character.
// Assumes that all characters in the str are from '0' to '9' or '-'. Will
//  return wonky numbers otherwise.
// Returns 0 if str == NULL.
int strToInt(const char* str)
{
    if(str == NULL)
    {
        return 0;
    }
    
    int stringLength = 0;
    int returnValue = 0;
    int multiplier = 1;    
    int stopPoint = str[0] == '-' ? 1 : 0;
    
    // Find the length of the incoming string
    while(str[stringLength] != 0)
    {
        stringLength++;
    }
    
    // Back up one so that stringLength indexes the least significant character
    stringLength--;
    
    while(stringLength >= stopPoint)
    {
        // Use the ASCII value for '0' as the base - the ASCII value of the char
        // at str position stringLength
        returnValue += (str[stringLength] - '0') * multiplier;
        
        multiplier *= 10;
        stringLength--;
    }
    
    // Handle the case of a negative number
    if(stopPoint == 1)
    {
        returnValue *= -1;
    }
    
    return returnValue;
}